As a method for producing azoline compounds, particularly for example oxazoline compounds, a method for cyclodehydration by heating an amidoalcohol in the presence of a catalyst is known, and various catalysts have been proposed. As the catalysts, for example a tin alkanoate has been used in JP-A 60-246378, an iron salt has been used in JP-A 56-128772, and an organic acid salt of zinc has been used in U.S. Pat. No. 4,354,029.
In these methods using an amidoalcohol, however, a substituent at the 2-position of oxazoline compound as a product is determined depending on the type of an acyl group on the amino group of amidoalcohol as a starting material, so there is a problem that it is difficult to produce various oxazoline compounds.
A method of reacting an alkanol amine with nitrile in the presence of zinc acetate as a catalyst has been proposed in JP-A 59-21674. In this method, however, there is a problem that the yield is low unless the reaction temperature is high (about 190° C.).
Synlett, 2005, 15, 2321 has been described a method for producing a bisoxazoline compound from a dinitrile and an amino alcohol using zinc trifluoromethanesulfonate. JP-A 2002-275166 has been described a method for producing a cyclic imino ether (oxazoline compound) from a nitrile and an amino alcohol by using basic zinc acetate as a catalyst. However, nitrile as a starting material may be hardly obtained, and therefore, a method using a carboxylic acid or a carboxylate which is more easily obtainable than a nitrile in place of nitrile has been also examined.
For example, Org. Lett., 2002, 4, 3399 has been described a method for producing an oxazoline compound from a carboxylic acid and an amino alcohol by using stoichiometric quantities of triphenyl phosphine/carbon tetrachloride. J. Comb. Chem., 2002, 4, 656 has been described a method for producing an oxazoline compound from a carboxylic acid and an amino alcohol by using 3-nitrophenylboronic acid as a catalyst.
As for a method using a carboxylate as a starting material, Tetrahedron Lett., 1997, 38, 7019, for example, has been described a method for producing an oxazoline compound by using an equivalent amount of n-butyl lithium and a catalytic amount of a lanthanoid compound such as samarium chloride. Further, Tetrahedron Lett., 1990, 31, 6005 has been described a method for producing oxazolines by using dimethyltin chloride as a catalyst after dehydration reaction of diethyl malonate and an amino alcohol.
As a method for producing an amide compound and peptides, various production methods have been known, and examples of such methods include a method comprising the steps of heating a carboxylic acid or a carboxylate and amines and removing the formed water or alcohol out of the system, a method of using a condensation agent such as dicyclohexyl carbodiimide, and a method of using a Lewis acid (see Synlett, 2005, 15, 2321). In these methods, however, there are problems that, for example, heating at high temperature and an excess of a condensation agent are required.